We have found that narcissus alkaloids (pretazettine and pseudolycorine) have a remarkable anti-leukemic activity against Rauscher viral leukemia and a moderate anticancer activity against several transplantable (non-viral) tumors in mice. This project is for the further basic studies of the alkaloids, especially the mechanisms of therapeutic activity at enzyme, cellular, and animal levels, evaluation of the therapeutic activity against spontaneous AKR leukemia as a better model of human lymphocytic leukemia, establishment of the best treatment-schedule including the combination with standard anticancer drugs or other investigative agents, prevention of viral expressions and finally eradication of the viral genomes from the chronically virus-infected cell lines and animals, pharmaco-toxicological studies in bigger animals and synthesis of more active derivatives of the alkaloids by massive production of the alkaloids, and studies of chemical structure-biological activity relationship, etc. to be completed before any future clinical application.